The present invention relates to a sheet conveyance device which conveys a sheet.
Conventionally, as a sheet conveyance device which conveys a sheet, a sheet conveyance device which includes a sheet reversing unit and is applied to a sheet-fed offset rotary printing press equipped with a reversing mechanism and capable of printing on one or both of the two surfaces of a sheet, has been proposed, as described in Japanese Patent Laid-Open No. 58-219058 (literature 1). In the printing press proposed in literature 1, a sheet conveyance device including a reversing unit is interposed between first and second, adjacent printing units, and performs a selective reversing operation for a sheet conveyed by the sheet conveyance device to allow single-sided printing and double-sided printing on the sheet.
In the printing press described in literature 1, the reversing unit includes a transfer cylinder (reference numeral 17) and impression cylinder (reference numeral 16). In double-sided printing, the trailing edge of a sheet conveyed while the leading edge of the sheet is gripped by the transfer cylinder is gripped by the impression cylinder to convey the sheet with its trailing edge leading, and turn it.
However, in the printing press described in literature 1, when the sheet size is changed, engagement of a gear which drives the impression cylinder is canceled before activation of the printing press, the phase of the impression cylinder relative to the transfer cylinder is changed so that a gripper device of the impression cylinder is opposed to the trailing edge of the sheet held on the transfer cylinder, and then the gear must be engaged again. This increases the operator's burden, and its preparation takes a considerable time.